FR2680170A1 - PYROLYSIS OF MIXTURES OF NATURAL CRYSTAL ACIDS TO ELIMINATE ALCOXYAROMATIC IMPURITIES. - Google Patents

Abstract

A process for removing guaiacols from naturally-occurring cresylic acid mixtures by pyrolysis is described.

Description

Py

  The present invention relates to a method of eliminating

  alkoxyaromatic impurities, in particular galacol, from natural cresylic acid

by pyrolysis in the vapor phase.

  Cresylic acid is an important industrial product commonly used in the manufacture of chemicals, agrochemicals, pharmaceuticals and industrial intermediates.

  lower molecular mass, namely phenol, is

  synthetically synthesized on a very large scale.

  The three cresols are also produced synthetically,

  but in much smaller amounts dimethyl-

  phenols (xylenols) and other alkylated phenols are not

  industrially synthesized to a significant degree.

  recovery from natural sources such as partially refined oil and coal

  baking, gasification and liquefaction is the

  part of the cresylic acid used today in the industry.

  The cresylic acids that are recovered from these

  sources are heavily contaminated with organic compounds

  aromatic hydrocarbons, as well as those containing hetero atoms such as nitrogen, sulfur and oxygen atoms. Methoxy-substituted phenols are a very

  some low quality coal, such as coal

  good red or lignite Guaiacol, which is a methoxy-

  phenol, has a boiling point close to that of meta and para-cresols, whereas methyl-galacols, ie methoxy-cresols, have boiling points close to those of xylenols Consequently, guaiacol does not can be separated from the cresylic acid fractions by conventional distillation For the sake of utility, the various isomers of cresylic acids must be separated from other impurities and frequently from each other and this is where the problem lies because so far, we

  did not know any simple process to separate physical-

  Guaiacic Acid Guaiacols accordingly,

  guaiacol must be destroyed in the presence of cresylic acid

  that also poses the problem of a loss of

  The mixture of cresylic acids

  raw materials obtained from lignite contains

  the highest proportions of galacol that the mixture obtains

  from coal, up to almost 4% by weight or more Until now, such destruction could be done with difficulty and the resulting loss of cresylic acid gives byproducts most of which

  are unwanted heavy products and coke.

  Considerable academic research has been conducted on the removal of methoxy compounds or the demethylation of phenols. This work is described in such articles as Lawson, J and M Klein, "Influence of Water on Guaiacol Pyrolysis", Ind Eng Chem. . Fundam, 24: 203, 1985; Ceylan, R and J Bredenberg, "Hydrogenolysis and Hydrocracking of the Carbon-Oxygen Bond in Guaiacol", Fuel, 61: 377, 1982, and Vuori, A and J. Bredenberg, "Hydrogenolysis and Hydrocracking of the Carbon".

  Oxygen Bond 4 Thermal and Catalytic Hydrogenolysis of 4-

  propylguaiacol ", Holzforschung, 38: 133, 1984.

  Lawson's article studies the pyrolysis at 383 C of gafacol, pure or in the presence of water to study the effect of the presence of water on calcination and formation of water.

  by-products during pyrolysis.

  products to verify the information provided in the

  Ceylon and Vuori ticles cited above We use reactors with successive charges, galacol of purity

  98% and isothermal conditions.

  actor of the source of heat after reactions of a duration of 15 to 90 minutes, one cools with water and one

  analyzes the products The presence of water reduces the

  coke, but also results in a higher yield of catechol, while the yield of o-cresol

  decreases as the amount of added water is increased.

  The article confirms that during fission, it is the weakest phenyl-methyl bond that breaks

  phenol and methane as a product However, the

  deresse has established that pyrolysis at the temperatures

  born in the articles does not reduce the composition of galacol in a charge stream of crude cresylic acid

  from coal and much less from lignite.

  Such an academic discussion does not therefore facilitate the development of a method for eliminating galacol from

  such charge currents in order to recover the cresylic acid

  In the prior art, the problem of by-product formation during the reaction of such hydrogenated streams is well indicated, but

real solution to this problem.

  Accordingly, the subject of the present invention is a method of removing galacol from

  supply streams of crude cresylic acid.

  The present invention thus provides a process for removing methoxyaromatic impurities from a vaporized feed stream of natural mixtures of cresylic acids which comprises: passing the vaporized feed stream through a heated tubular reactor at a rate of temperature of at least about 450% C under pyrolysis conditions to form a pyrolysis product stream, to cool the stream

  pyrolysis product to stop the formation of sub-

  products and condense the cresylic acid, to draw off the non-condensable gaseous compounds from the product stream of

  cooled pyrolysis and recovering the cresylic acid from

shooting of such a product stream.

  The present invention also provides a

  method of eliminating galacol from a natural mixture of cresylic acids which comprises: filtering the mixture of cresylic acids to remove pitch; distilling the mixture to remove phenol and low boiling impurities; spraying the mixture of cresylic acids free of pitch and phenol and containing galacol;

  passing the vaporized mixture through a tubular reactor

  heated to a temperature of 530 to 5800 C under pres-

  atmospheric deposition at a space velocity of 0.6 to 1.2 per hour to pyrolytically convert substantially all of the gaiacol into pyrolysis products leaving the cresylic acid mixture substantially free of guaiacol; cooling the mixture of gafacol-free cresylic acids with a stream of a mixture of cooled cresylic acid in a condenser vessel

  cooling to stop the formation of sub-

  pyrolysis products and to condense the cresylic acid; withdrawing a stream of uncondensed gases from the cooling condenser container in the form of a

  head stream and the condensate flow of

  se in the form of a tail stream; to cool the neck

  trailing at a temperature of 55 to 650 ° C to form a cooled cresylic acid mixture; to recycle a portion of one-quarter to three-quarters of the cooled mixture of cresylic acid to the condenser container and to

  recover the rest of the cresylic acid.

  Other peculiarities and advantages of

  will be apparent from the following description of the modes

  preferred embodiment of the invention with reference to the accompanying drawing, in which: FIG. 1 is a general diagram of a preferred embodiment of the invention not representing the usual components such as pumps, valves and corresponding instruments ; and

  FIG. 2 is a representation, partially

  in schematic form, showing the equipment of

  test for carrying out the examples of the invention.

  The invention relates to pyrolysis in the vapor phase.

  afraid of natural mixtures of cresylic acids that

  cup of residual pitch when removing liquids from coal, coal tars, lignite or natural gas condensates These natural mixtures containing cresylic acid contain various methoxyaromatic impurities, in particular galacol, which is found

  frequently in amounts up to 4% O and,

  even about 6% by weight when the materials come from

  from a source of lignite and about 2% o when the

  The mixture of cresylic acids forming the feed for the implementation of the invention comes from coal or a

  Coal tar The process according to the invention

  It can not be effective in removing even greater amounts of guaiacol from the natural loads and should not be considered as limited to 4% by weight.

  The presence of such methoxyaromatic impurities

  significantly reduces the industrial value of cresylic acid as a raw material for

  high quality plastics and resins.

  The raw load is then treated to extract the pitch

  and distilled to remove phenols and low-boiling light hydrocarbons, ie materials with lower boiling points

  or close to those of the phenol being racked.

  In the practice of the invention, the filler is vaporized in various ways well known to those skilled in the art and is admitted into a tubular reactor heated externally in a manner very similar to that of water vapor in a tube. boiling or in thermal cracking apparatus operations, such as thermal cracking

  naphtha to obtain methylene in a boiler.

  The material which is preferably used for the tubular reactor is steel, preferably stainless steel, so that the vapors flow smoothly through the heated zone. Optionally, the tubular reactor is filled with an inert lining such as beryllic saddles, steel tower liners and the like to facilitate uniform heat distribution Tubular reactors can be oriented so that their longitudinal axis is horizontal

  or vertical as long as the heating remains uni-

form.

  The reactor is operated at a temperature of

  at least approximately 4500 ° C, provided that the other conditions, ie pressure and flow,

  at satisfactory pyrolysis conditions at temperatures

  from about 475 to 625 WC, preferably from about 500 to 600 WC, and more preferably from about 530 to 58 Qa C. For the process according to the present invention, the pyrolysis conditions comprise a temperature of about 475 to 6250 C, the pressure is preferably from about atmospheric pressure to about 4.053 bar (4 atm) and the hourly space velocity in the tubular reactor

from about 0.5 to 2.0 per hour.

  In the process according to the present invention, adjusted so as to maximize the elimination of ga Tacol,

  the temperature is more preferably

  taken between about 530 and 5800 C, the pressure is about atmospheric and the linear hourly space velocity is

from 0.6 to 1.4 per hour.

  When the process is adjusted so as to maximize the flow rate of the charge, the temperature is preferably between about 575 and 6000 C, the

  pressure is between 2,026 and 4,053 bar (2 and 4 atm) and the

  Linear hourly tialè is about 1.7 to 2 per hour.

  In addition, in order to minimize the

  coke, the vaporized charge stream preferably includes

  at least about 3% by weight of water.

  Finally, and advantageously, the method according to the present invention also comprises stages of

  cooling of the cooled pyrolysis stream, and

  recycling a sufficient amount of the cooled pyrolysis stream to cool the pyrolysis product stream.

  Temperature and flow are the two main variables

  the process of ensuring the destruction of guaiacols and

  their subsequent elimination It has been found that the conditions

  The optimum pyrolysis rates of guaiacol in phenol-free cresylic acid from a lignite source are at about 5500 C and a liquid hourly space velocity (LHSV) of 0.6 to 1.4 hl. 1 and especially 1 hour A minimum temperature of about 5300 C is required to reduce guaiacol to undetectable values (less than 10 to 20 ppm) at a WHSV of 0.6 hl when the temperature falls below of

  450 C, the amount of guaiacol increases and only 2,% o

  die in the reaction product after a reaction at about 4000 C so that it is very unattractive and

  almost futile to use such a low temperature.

  Other factors determine satisfactory conditions

  pyrolysis and can be adjusted using

  economically and industrially satisfactory.

  High temperatures can be employed, but the pressure and

the flow rate.

  The maximum flow rate which regularly ensures an almost complete elimination of guaiacols at 530 ° C. under atmospheric pressure is a LHSV of 0.6 h. Table A shows that unreacted guaiacol in m, p-cresol at 5300 C increases from a non-detectable value to less than 0.02% o when the space velocity is increased from 0.6 to 1.2 hl A rise in the space velocity to 1.7 h 1 increases

  even more guaiacol in the product up to 0.10%.

  Complete removal of the Gatacol at a GLSV of 1.7 h 1 is only possible if the reactor temperature is raised to 600 C. However, the higher flow rates made possible by high temperature operation are only

  price of higher production of coke and gas.

  The formation of coke increases from 0.1 to 0.4% and the production of gas more than doubles when the reaction temperature is raised from 540 to 6000 C (Table A). The light neutral by-products double in quantity, the phenolic by-products increase by 25% and heavy by-products

  (dibenzofuran C 12) do more doubling.

TABLE A

  By-products of galacol pyrolysis

VSHL 0.6 h 1 (%, by weight).

  at 5400 C and a m, p-cresol filler product based coal filler product made from lignite filler product traces 0.3

32.5 34.0

24.5 26.3

o-cresol m, p-cresol

2,4 / 2,5

  xylenol 0.1, 8 0.7 97.0 traces 0.2 other CA 0.1 heavy / Alc galacol catechols 0.2 0.1

12.4 12.6

3.6 2.5

  2.0 4.0 e 0.9 3.9 0.8 1 Neutral oils and nitrogen bases whose

lower for phenol.

  boiling points are Source light products phenol 0.3 0.6 0.7 1.0 14.8 29.5, 2 29.4 17.4 46.1

, 2 5,4

  18.0 46.4 2.8 2.9 4.5 0.8 4.4 1.1 1.1 The range of pressures for the pyrolysis of the

  present process is between about the pressure

  mospheric up to approximately 4.053 bar (4 atm), preferably a

  The operation of the pyrolysis process at a low pressure of between approximately 0.28 and 0.84 bar at the gaseous pressure has a favorable effect on the elimination of the gajacols. Operation under pressure significantly increases the elimination of gajacols by having little or no effect on gas production, but

  as a result a stronger formation of coke.

  This is the anticipated result as the length of stay is increased when operating under pressure (ie

  say that doubling the system pressure while maintaining

  constant mass flow would have the effect of reducing

  50% volumetric flow rate) which allows the use of higher flow rates or lower operating temperatures while ensuring the elimination of galacol of the same

  type that is obtained under atmospheric pressure.

  Equipment dimensions in an industrial process

  can also be reduced when operating under

  if we. The composition of the cresyl acs influences the efficiency of the removal of galacols and the by-products The formation of by-products is much less obvious when a mixture of

  mp-cresols instead of a complete charge of acids.

  Total removal of galacols from cresylic acid

  phenol-free lignite (4% galacol) is a little more

  difficult only from mixtures of m, p-cresols containing guaiacol

  for a coal test or charge.

  The m, p-cresol treated at 530 C and 0.6 H LHSV contains no detectable residues of galacol, while the lignite filler similarly treated in

  similar conditions contains 150 ppm of guaiacol.

  Similar results are observed when changing temperatures and space velocities as can be seen in Table B. Effect of charge,

galacols.

Table B

  temperature and flow on the 1 eli-

  Load matrix o of gaiacol temp. o C Gaiacol in product%

VSHL VSHL

  0.6 h-1 1.2 h-1 m, lignite-based lignite based p-cresol * LHSV 1.7 h 1 NA 1 NA 0.018 none NA NA 0.101 0, 006 none 3 , 9 3.9 0.441 0.051 none 2 none none none 0.015 0.001 0, 009 NA NA NA

0, 183

  0.008 0.031 nil NA NA NA nil 1 NA = not analyzed 2 nil = less than a minimum detectable limit (less than

at 20 ppm).

  The amount of the exhaust gas and coke produced is proportional to the concentration of guaiacol

  In the load When comparing the coal-based load

  the lignite-based charge, a doubling of the content

  Guaiacol in the load more than doubles the training

  Even though the quantity of the exhaust gases doubles, the formation of gas per kg of treated gaiacol is the same for the two charges. A smaller quantity of gas is formed per kg of guaiacol when the source is m, p-cresol only in the case of a total charge

  of acids A small amount of coke and

  from a coal-based feed that does not contain guaiacol under pyrolysis conditions confirms that by-product gases are due to cleavage of guaiacol

  rather than the decomposition of cresylic acid

  lume gas increases by a factor of 1 when treating a coal-based filler containing 2% o guaiacol and coke increases from an undetectable value to about 0.1% of the filler, as can see this in

Table C.

Table C

  Formation of coke and gas from the pyrolysis of gaiacol charge matrix coal coal lignite guaiacol 0, d O env 4 temp OC ol o coke in charge gas dm 2 / kg of galacol -0- env O, 1 env 0, 3

164.36

163.74

  m, p-cresol m, p-cresol ca 0.1 to about 0.4, 16

296.35

  Water may be present in the cresylic acid feed as it enters the reactor or may be added to the acid feed stream

  to inhibit the formation of coke even though its

  the risk of slightly preventing the conversion of

  In the context of the invention, water may constitute

  to kill 3% by weight or more, the final quantity being

  undermined by economic and industrial considerations

  within the preferred range of about 5 to 12% by weight.

  After describing the various parameters of the method of the invention, reference will be made to FIG. 1, in which a preferred embodiment has been shown.

of the invention.

  The charge is admitted in an oven 10 by a stream 12 of raw charge In this embodiment, the oven 10 runs on oil such as for example the natural gas, introduced through the lines 14 and 16 into burners not shown. any number of oil intake points are commonly used, two are shown here, the fuel being admitted through line 14 to heat a vaporization zone 18 in which the gross load admitted by line 12 is vaporized. evaporated crude cresylic acid containing guaiacol passes through the vaporization zone 18,

  by the tubes 19 to exit by a pipe 20 and it can-

  follows its path to a separator drum 22 in which the vaporized charge is separated from a residue which leaves the

  drum 22 by a pipe 24 for evacuation or use.

  The vapors leave the drum 22 via a pipe 26 and

  return to oven 10 to reach a zone of pyrolysis

  lysis 28 in which the vapors are introduced into a

  tubular reactor 30 in the pyrolysis zone 28.

  It is here that with operation under the previously described pyrolysis conditions, galacol and other methoxyaromatic products are converted

  in a pyrolysis reaction or degradation products.

  The pyrolyzed vapor stream exits the pyrolysis zone 28 via a line 32 which transfers it to a cooling condenser 34. The pyrolysis products are here

  brought into contact with the cooling current, pre-

  the condensed and cooled cresylic acid allowed in

  the cooling condenser 34 by a pipe 36.

  The main purpose of rapid cooling is to stop all the reactions that take place in the pyrolysis and

  liquefaction of the cresylic acid.

  In the practice of the invention, surprisingly low amounts of by-products are formed and the loss of cresylic acid is very low. Non-condensable gases such as for example carbon monoxide, methane and nitrogen leave the cooling condenser 34 via a pipe 38 for appropriate evacuation

  in the environment with cooled cresylic acid

  both of the cooling condenser 34 by a tail pipe 40 in the form of liquid and then going into a condenser 42, preferably cooled with water, on its side envelope o the product stream undergoes a new cooling of a value of d approximately 55 to 700 C. This temperature is not critical, but the use of

  this narrow range has proved effective in

  The cooled cresylic acid exits the heat exchanger 42 through line 44 in a form substantially free of galacol-type impurities and continues on its course.

  by the pipe 36 o a portion is recycled on the basis of

  The amount of the cooled mixture of cresylic acids to be recycled is easy to calculate using the thermodynamic properties of the current of the

  pyrolysis product which is still available to a qualified engineer

  Usually, the recycled quantity is between about 1/4 and 3/4 of the current coming out of the heat exchanger.

  heat, the recycling taking place to the condenser 34.

  Preferably, the amount recycled is about 40 to 60%

  according to the thermodynamic properties of the current.

  A treated product of cresylic acid substantially free of annoying galacol, is discharged from the pipe 44 by a pipe 46 and is then brought into a reservoir in order to

  additional treatment before sale or employment.

  The cooling condenser 34 operates at a pressure substantially atmospheric or below atmospheric to improve the evacuation of gases

  Exhaust and non-condensable vapors

  The aim of this treatment is to stop the pyrolysis reaction in order to prevent the formation of by-products and the reduction of cresylic acid which would otherwise be lost.

  due to the formation of a heavy product stream.

  The treated product leaving the line 46 can then be further refined by a flash distillation, which is not shown. The recovery of treated products

  relaxation distillation confirms the absence of a forma-

  high boiling point products during the pyrolysis process according to the invention and also that by vacuum expansion distillation of the pyrolysis products of two coal-based charge samples.

  containing O and 2% of galacol, respectively, ensures a

  distillate intake of more than 99.99% and 99.1%

  The relaxation distillation normally takes place

  at about 0.1333 bar (100 mm Hg).

  The invention described above will be studied with

  more precision when describing the equipment of

  test that appears in Figure 2 and the process by which the invention was developed It is understood that the equipment, the stages of the process and the sequence by which these stages

  may be varied or modified without departing from

  the framework and spirit of the invention.

* Pyrolysis in the vapor phase is carried out in the galacol tests in a steel reactor tube 110

  316 stainless steel having 19 mm inner diameter and 711 nm

  of length that we see schematically in Figure 2.

  The pipe is lined with inert materials 112 (stainless steel lining, glass beads, or Mg O pellets) providing heat transfer. A fluidized sand bath 114 maintained by an outer pipe 115 and heated by two heating devices 116 The 1500 watt nichrome heats the reactor 110 and provides equal temperature control. The air for fluidizing the sand bath is admitted via a line 118 and is preheated to a temperature of 500 600 in an air line.

  2.5 x 30 cm lined with alloy beveled fibers 20

  placed in a furnace 119 of the Lindberg tubular type.

  Thermocouples 120 measure the temperature of the sand and the temperature of the reactor. The feed stream 122 joined by an optional stream of air or diluent nitrogen 123 is pumped into the reactor 110 using a Series 2 MPL micropump ( not shown) at a flow rate of 100 to 300 ml / h

  to perform the test described later.

  The feed intake duct 122 passes through the heated sand 114 and the feedstock is vaporized. The feedstock is admitted into the tubular reactor 110 through its base 11a, which passes through the packing 124 of the stainless steel column and back through the reactor tube in the pyrolysis zone II Ob The top of the tubular reactor 11 Oc is lined with alloy fibers 126

  (Carpenter Steel Co) The pyrolyzed product comes out of

  puts reactor II Oc through a pipe 128 and is condensed

in the condenser 130.

  The vaporized product from reactor 110 is cooled

  in the condenser 130 and is collected for the purpose of

  lysis in the product receptor 132.

  The exhaust gases are measured in some tests using a wet measuring apparatus 134 having 28 cm graduations. The apparatus is operated at the laboratory scale as described above by pumping the load. of cresylic acid / galacol through a rotameter in a preheating and reaction zone within the heated sand bath 114, then cooled in the condenser 130 and the treated product collected in the

  Receptor 132 The pressure tests are carried out using

  reading a pressure point relief valve

  variables 136 so as to maintain a manometric pressure

  than about 2.1 bar gauge.

  The distribution of isomers of cresylic acids is measured

  as well as the content of neutral oils

  1.5 liquid gas chromatography using methods

  The residues are determined on composite samples.

  selected by expansion at 0.1333 bar (100 mm Hg) up to

  where the head temperature begins to fall (generally

  C. The remaining residue is weighed into the flask and is presented as a percentage of the charged cresyl products. The formation of coke is calculated by weighing the tubular reactor before and after the test, the possible acid residual cresylic having been removed from the

  system by steam purging While the

  transferred and the devices described above are used to

  perform the tests described in Examples I to IV which follow

  Alternatively, other comparable methods and appropriate instruments known in the art can be used.

Example I

  A mixture of m, p-cresols containing 4% of guaiacol was prepared and passed through a vaporizer assembly and a tubular reactor packed with an inert material for heat transfer as described above and shown in FIG. The reactor is heated in a fluidized sand bath at a temperature of 500 to 600 ° C. and the reaction is carried out under atmospheric pressure.

  of cresylic acid corresponds to a VSHL of 0.6 to 1.7 h-1.

  The treated product leaves the reactor and is passed through a condenser, then collected for analysis.

  The following summarizes the test data at various temperatures.

tures and space velocities.

  Gaiacol in the product Temp C 0.6 h-1 1.2 h-1 1.7 h-1% coke in charge

500

  0.44 0.05 NA NA N / A ** 0.02 N / A NA NA NA NA Approx 0.1 0.10 NA NA Env 0.4 Gas Dm 3 / kg Galacol NA

118.29

N / A

298.84

  * not analyzed ** not detected The by-products of the reactor include 1, 7% other phenolic products, 0.3%, light products, 0.1% heavy products,

and 0.9 catechols.

Example II

  Cresylic acid based on

  coal containing about 4% galacol (added to

  a mixture) through the reactor in the same manner as in Example I at 530 ° C. to obtain 0.02 ° of unreacted galacol at a WHSV of 0.6 h 1 and 0.18% of galacol at 1.2 h -1 The treatment of the cresylic acid coal feed at 550 C reduces the amount of galacol to trace amounts at 0.6 h 1 and at a value of less than 0.01,% at 1.2 h -l

Example III

  With the same equipment and test method as above, several operations are performed to determine the optimal conditions for complete pyrolysis of the galacol. Factors influencing the

  coke formation in order to study the conditions in

  the coke is not made There are three types of tests:

  1 stainless steel reactor having a

  m-cresol gacol-added, 2 stainless steel reactor with a phenol-free lignosilic acid feed removed from phenol and

pitch.

  3 quartz reactor arranged as on the

  gure 1 with m-cresol charge plus galacul The quartz reactor configuration is similar

  to that of the stainless reactor described above.

  The reactors are operated under isotonic conditions

  the condenser by wrapping hot ribbons

  and using an additional temperature regulator. The charge in this example is a meta-cresol supplemented with galacol so that the products of pyrolysis of guaiacol can be differentiated and the losses

  yield of cresylic acid are easier to calculate.

  The effects of pressure and tempera-

  When the pressure is varied, we do not try to maintain the residence time at a constant value

  By varying the flow rate In this example, the differences

  pressure tests show the effects of pressure and variations in residence time The actual residence time in the reactor assuming ideal behavior

  gas is 19 to 20 seconds for pressure testing.

  atmospheric pressure and durations from 51 to 53 seconds for

  tests at a pressure of 1.7 bar.

  Pressure and temperature are varied in

  In the steel reactor at 500 ° C or 4700 ° C and a gauge pressure of 1.7 bar

  almost total withdrawal of galacol A 4700 C and under

  atmospheric pressure, the elimination of galacol falls to 91.6%.

  The yield loss in cresylic acid is 4 to 5%

in these last conditions.

  In Table I, the pyrolysis tests are summarized.

Table I

  Galacol Vapor Phase Racking Summary Temperature C Reactor Air Sand Bath Top of

condensing

Pressure pressure bar charge background

condensing

sor

exhaust gas

  charge * cm / g load flow (l / min) load product load (gai) O, o Column Column stainless steel

500,438

500 488

470 470

470,468

  quartz 1.75 o O 1.68 1.83 1, 82 o W, 8 3.9 3.9 13.9 6.76 6.84 6.81 6, 51 3.0 6.72 6.38 6.69 6.61 6.27 6.46 3.43 3.42 3.37 3.37 3.37 All tests in this table use meta-cresol with addition of guaiacol * noncondensible gaseous products are primarily methane and carbon monoxide K) MGF "II G Table I (continued) products (.0%) Phenol Catechol Heavy Removal of guaiacol (%) Meta-cresol% by weight Charge product loss in steel 0.91 0 , 61 0.31 0.74 stainless

0.56 2.48

0.90 2.44

0.88 2.19

0.54 2.75

  99.8 99.6 91.6 99.8 94.9 94.9 94.9 94.9, 1, 8, 9 91.2, 1 4.3 4.2 3.9 i J Quartz column 0 , 41 0.89 2.03 96.5 K) Galacol Analysis Column 0.01 0.01 0.28 0.01 0.12

  The following conclusions can be drawn from the

  test results: 1 the conversion of guaiacol is almost 100 o for three of the four conditions used 5001 C at 0 and 1.75 bar at the gauge and 4700 C at 1.68 bar at 4700 C and under atmospheric pressure, the conversion of Guaiacol drops to 91.6% o

  2 the loss of meta-cresol yield is es-

  sensibly constant between 4 and 5% during the study.

  The losses are very low when we feed the reactor

  in pure m-cresol and no guaiacol.

  3 the amount of catechol produced is higher

  under atmospheric pressure at 1.75 bar, the quantity

  of phenol produced is higher than under

mosphérique.

  4 the formation rate of non-condensed products

  seems to be a function of pressure (and / or length of stay) and is not influenced significantly by

  reactor temperature Non-condensable products

  present about 1% O of the load.

  methane and carbon monoxide are the gases

non condensables.

  6 the quantity of heavy products obtained is essentially constant between 2.2 and 2.8% o at all

conditions studied.

  The complete range of

  sylics free of lignite pitch in the

  stainless steel actor for two tests at 5000 C and 1.75 bar manometer and with results similar to

  those obtained with m-cresol supplemented with guaiacol.

  The conversion of guaiacol under these conditions is total.

  The accumulation of coke occurs in the

  quartz actor The rate of formation of the

  coke as 0.011% by weight of the filler.

Example IV

  These tests are carried out in the pre-

  described above using the same techniques for

  find the effect of water to reduce or eliminate coke formation Water is frequently added to

  pyrolysis reactors to reduce coke formation.

  Galacol in meta-cresol is pyrolyzed in two regions.

  actors in stainless steel at 5000 C and under pressure

  mospheric and in a quartz reactor using three different ratios of water to cresylic acid: O, 0.18 and 1.0 by weight The rate of formation of coke

  in these three cases is 0.12%, 0.07% o and 0.01% o respec-

  compared with the load The elimination of galacol is more than 96% in all three cases, although the residence times in the reactors are not maintained at constant values due to the absence of

  the important effect of water on the volume of the steam.

  Operations with a high water ratio have a shorter residence time than in the other two tests. Losses of yield appear to be less with the addition of water, although the differences in yield losses between the different conditions are within the experimental error The rate of release of gas

  exhaust and heavy product formation varies slightly

  between two different conditions, but one

not noticeable way.

  Increasing proportions of water increase the relative amount of exhaust and reduce the quantities of catechol, heavy products and coke.

  quantities of exhaust gas, catechol and

  heavy dudes are relatively low, but the

  The formation of coke is very important.

  Coke formation decreased by about 40% at a ratio of 0.18: 1 e / c (water / cresol), from 0.12 to 0.07%, compared to the example without water and more low about

  90% o of coke is formed at an e / c ratio of 1: 1.

  The addition of water does not seriously reduce the reaction rate Galacol conversion is higher during tests with a 0.18: 1 e / c ratio than in tests without the addition of water.

  ratio of 1: 1 produces the same conversion as the

  know without water, even if the length of stay is 3 to 4

  times shorter with the addition of water.

  The addition of water to the reactor appears to reduce the losses of total yields of cresylic acid and meta-cresol, although the differences are within the experimental error Under equivalent operating conditions, 5000 C and atmospheric pressure, the losses of yield are greater in the steel column

  only in the quartz column, although the

  are once again within the error of experience

  The residence times and conversions of galacol are slightly different between the two reactors 19 S and 99.6% conversion for the steel reactor

  stainless steel and 15 S and 96.5% conversion for the re-

quartz actor.

  The above study shows that pyrolysis

  lysis is a simple and effective method for removing galacol from a lignite-based filler as well as

  other natural sources of cresylic acid.

  improve the benefits of the process by adjusting the conditions

  according to the method described to ensure an eli-

  complete galacol mining, small losses in

  cresylic acid and low formation of sub-

  products. While under certain conditions, the formation of coke is the result of the implementation of the invention,

  considering the above study and examples, we can ap-

  many modifications to the processes and the operating conditions, which is within the reach of those skilled in the art, in order to obtain varied results according to the needs and specific objectives without departing from the scope

  of the invention defined by the appended claims.

Claims (9)

  1 Method for removing methoxy impurities   aromatics from a vaporized feed stream of natural mixtures of cresylic acids, characterized in that it comprises: passing the vaporized feed stream through a tubular reactor heated to a temperature of at least about 4500 C under pyrolysis conditions to form a pyrolysis product stream, to cool the stream   pyrolysis product to stop the formation of sub-   products and condense the cresylic acid, to draw off the non-condensable gaseous compounds from the product stream of   cooled pyrolysis and recovering the cresylic acid from shooting of such a product stream.   Process according to claim 1, characterized   in that the pyrolysis conditions comprise a temperature of about 475 to 6250 ° C., a pressure of about 20 ° C. at atmospheric pressure to about 4.053 bar (4 atm) and a hourly space velocity in the tubular reactor of about 0.5 to 2.0 per hour.   Process according to Claim 2,   characterized in that the temperature is between   530 and 5801 C, the pressure is approximately atmospheric and the linear hourly space velocity is 0.6 to 1.4 on time.   4 Process according to claim 2,   characterized in that the temperature is between   at around 575 and 6000 C, the pressure is between 2 and   4 atm and the linear hourly space velocity is approximately   1.7 hours per hour or higher.   Process according to any one of Claims 1 to 4, characterized in that the charging current   vaporized comprises at least 3% by weight of water approximately.   Process according to any of the claims   tions, characterized in that the reactor tu-   bung is made of stainless steel and is lined with inert packing.   Process according to any one of the claims   cations, characterized in that it also includes   the cooling stages of the pyrolysis current   cooled and recycled a sufficient amount of   pyrolysis reactor cooled to cool the pyrolysis.   A process for removing galacol from a natural mixture of cresylic acids, characterized in that it comprises: filtering the mixture of cresylic acids to remove the pitch; distilling the mixture to remove phenol and low boiling impurities; spraying the mixture of cresylic acids free of pitch and phenol and containing galacol; 2680170 '   passing the vaporized mixture through a tubular reactor   heated to a temperature of 530 to 5800 C under pres-   atmospheric deposition at a space velocity of 0.6 to 1.2 per hour to pyrolytically convert substantially all of the gafacol to pyrolysis products leaving the cresylic acid mixture substantially free of galacol; cooling the mixture of galacol-free cresylic acids with a stream of a mixture of cooled cresylic acid in a condenser vessel   cooling to stop the formation of sub-   pyrolysis products and to condense the cresylic acid; withdrawing a stream of uncondensed gases from the cooling condenser container in the form of a   head stream and the condensate flow of   se in the form of a tail stream; to cool the neck   trailing at a temperature of 55 to 650 ° C to form a cooled cresylic acid mixture; to recycle a portion of one-quarter to three-quarters of the cooled mixture of cresylic acid to the condenser container and to   recover the rest of the cresylic acid.